Debris Collection Device with Enhanced Circulation Feature

ABSTRACT

A debris cleanup tool uses an eductor principle to induce flow into a lower end to bring debris into a housing where the debris will either settle out or be screened out and the remaining fluid drawn up into the eductor with motive force for the eductor coming from clean fluid pumped down a tubular string from the surface. The eductor performance is enhanced with a surrounding sleeve on the eductor outlet that directs eductor exhaust flow into an annular passage oriented in a downhole direction. The exterior of the sleeve has passages to allow some of the flow to go uphole while the sleeve wall has ports through it to allow flow in the annular passage to cut through to outside the sleeve for passage uphole or downhole.

FIELD OF THE INVENTION

The field of the invention is debris collection devices for subterraneanuse and more particularly debris collection devices that use an eductorprinciple to draw debris laden fluid into a lower end using exhaustedeductor fluid where the ability of the eductor to draw fluid is enhancedwith an exterior annular path outside the tool housing.

BACKGROUND OF THE INVENTION

When a metal object, such as a section of casing, a packer, or a losttool, is to be removed from a well bore, the best method of removal isoften to mill the object into small cuttings with a mill such as a pilotmill, a section mill, or a junk mill, and then to remove the cuttingsfrom the well bore. Furthermore, a milling tool will often result in theremoval of scale, cement, or formation debris from a hole.

It is important to remove the cuttings, or other debris, because otherequipment subsequently used in the well bore may incorporate sealingsurfaces or elastomers, which could be damaged by loose metal cuttingsbeing left in the hole. Most commonly, the metal cuttings and otherdebris created by milling are removed from the well bore by circulatingfluid down the inside of the workstring and out openings in the millingtool, then up the annulus to the surface of the well site. This “forwardcirculation” method usually leaves some cuttings or debris stuck to theside of the well casing or well bore surface, and these cuttings ordebris can damage some of the tools which may subsequently be run intothe hole. Also, safety devices such as blow-out preventers usually havenumerous cavities and crevices in which the cuttings can become stuck,thereby detracting from the performance of the device or possibly evenpreventing its operation. Removal and clean-out of such safety devicescan be extremely expensive, often costing a quarter of a million dollarsor more in the case of a deep sea rig. Further, rapid flow ofdebris-laden fluid through the casing can even damage the casingsurface. Nevertheless, in applications where a large amount of metalmust be removed, it is usually necessary to mill at a relatively fastrate, such as 15 to 30 feet of casing per hour. These applications callfor the generation of relatively large cuttings, and these cuttings mustbe removed by the aforementioned method of “forward circulation”,carrying the metal cuttings up to the well site surface via the annulus.In some applications, such as preparation for the drilling of multiplelateral well bores from a central well bore, it is only necessary toremove a relatively short length of casing from the central bore, in therange of 5 to 30 feet. In these applications, the milling can be done ata relatively slow rate, generating a somewhat limited amount ofrelatively small cuttings. In these applications where a relativelysmall amount of relatively small cuttings are generated, it is possibleto consider removal of the cuttings by trapping them within the bottomhole assembly, followed by pulling the bottom hole assembly aftercompletion of the milling operation. The advantage of doing so is thatthe cuttings are prevented from becoming stuck in the well bore or in ablow-out preventer, so the risk of damage to equipment is avoided.

Some equipment, such as the Baker Oil Tools combination ball type Jetand junk basket, product number 130-97, rely upon reverse circulation todraw large pieces of junk into a downhole junk removal tool. Thisproduct has a series of movable fingers which are deflected by the junkbrought into the basket, and which then catch the larger pieces of junk.An eductor jet induces flow into the bottom of the junk basket. Thistool is typical, in that it is generally designed to catch larger piecesof junk which have been left in the hole. It is not effective atremoving small debris, because it will generally allow small debris topass back out through the basket.

Moreover, the ability of this tool to pick up debris is limited by thefluid flow rate which can be achieved through the workstring, from apump at the well site. In applications where the tool must first passthrough a restricted diameter bore, to subsequently operate in a largerdiameter bore, the effectiveness of the tool is severely limited by theavailable fluid flow rate. Additionally, if circulation is stopped,small debris can settle behind the deflecting fingers, thus preventingthem from opening all the way. Further, if this tool were to be run intoa hole to remove small cuttings after a milling operation, the smallcuttings would have settled to the bottom of the hole, making theirremoval more difficult. In fact, this tool is provided with coringblades for coring into the bottom of the hole, in order to pick up itemswhich have settled to the bottom of the hole.

Another type of product, such as the combination of a Baker Oil Toolsjet bushing, product number 130-96, and an internal boot basket, productnumber 130-21, uses a jet action to induce fluid flow into the toolladen with small debris. The internal boot basket creates a circuitouspath for the fluid, causing the debris to drop out and get caught oninternal plates. An internal screen is also provided to further stripdebris from the fluid exiting the tool. The exiting fluid is drawn bythe jet back into the annulus surrounding the tool. However, here asbefore, if this tool were to be run into a hole to remove small cuttingsafter a milling operation, the small cuttings would have settled to thebottom of the hole, making their removal more difficult. Furthermore,here again, the ability of this tool to pick up debris is limited by thefluid flow rate which can be achieved through the workstring.

Another known design is represented by the Baker Oil Tools Model Mreverse circulating tool, which employs a packoff cup seal to close offthe wellbore between fluid supply exit ports and return fluid exitports. A reverse circulating flow is created by fluid supply exit portsintroducing fluid into the annulus below the packoff cup seal, whichcauses fluid flow into the bottom of an attached milling or washovertool. This brings fluid laden with debris into the central bore of thereverse circulating tool, to be trapped within the body of the tool. Thereverse circulating fluid exits the body of the tool through returnfluid exit ports above the packoff cup seal and flows to the surface ofthe well site via the annulus. This tool relies upon the separation ofthe supply fluid and the return fluid, by use of the packoff cup sealbetween the fluid supply exit ports and return fluid exit ports. Toavoid damage to this cup during rotation of the tool, the packoff cupseal must be built on a bearing assembly, adding significantly to thecost of the tool. Additionally, here as before, the ability of this toolto pick up debris is limited by the fluid flow rate which can beachieved through the workstring.

As shown in FIGS. 1 and 2, originally in U.S. Pat. No. 6,276,452, arotating tool 8 has a drive sub 10 at its upper end, a plurality ofsections of wash pipe 12, 16, 18 connected to the drive sub 10, a screencrossover 14 and a triple connection sub 20 connected to the wash pipe,and a milling tool 22 connected to the lower end of the tripleconnection sub 20. The drive sub 10 is adapted to connect to a rotatingworkstring (not shown) or to a downhole motor (not shown) connected to anon-rotating workstring, such as coiled tubing, by means such as athreaded connection. The sections of wash pipe 12, 16, 18, the screencrossover sub 14, and the triple connection sub 20 serve as a separatorhousing. The uppermost wash pipe ejection port section 12, which isthreaded to the drive sub 10, incorporates a plurality of supply fluidexit or ejection ports 24 penetrating the wall of the wash pipe section12 at spaced intervals. The screen crossover sub 14, which is threadedto the ejection port section 12, serves to hold a tubular filter screen32 in place below the ejection ports 24, with the screen 32 extendingdownwardly toward the milling tool 22 at the lower end of the apparatus.A first wash pipe extension section 16 can be threaded to the screencrossover sub 14, if necessitated by the length of the screen 32. Asecond wash pipe extension section 18 is threaded to the first extensionsection 16. The triple connection sub 20 is threaded to the lower end ofthe second extension section 18.

The milling tool 22 is threaded to the lower end of the tripleconnection sub 20. A plurality of blades 23 are positioned at intervalsabout the periphery of the milling tool 22 for milling metal items, suchas casing or liner pipe, from the well bore. The lower end of themilling tool 22 can have a drift plate 25, which has a diameter close tothe inside diameter of the bore hole in which the milling tool 22 willbe used. The drift plate 25 serves to prevent metal cuttings fromfalling down the bore hole. One or more intake slots or ports 26 areprovided in the lower end of the milling tool 22 below the blades 23. Inapplications where the stuck pipe is not concentrically positioned inthe casing or well bore, it has been found that the drift plate 25 canbreak loose, so in such applications, a milling tool 22 without thedrift plate 25 is used, and a single intake port is located at thebottom of the milling tool 22, instead of a plurality of slots 26.

Importantly, a debris deflector tube 28 is threaded into an interiorthread in the triple connection sub 20, extending upwardly from thetriple connection sub 20 toward the screen 32. A plurality of side ports30 are provided through the wall of the deflector tube 28. A deflectorplate 31 is provided in the upper end of the deflector tube 28 todeflect any metal cuttings or other debris which might be carried byfluid flowing through the deflector tube 28, and to separate the debrisfrom the fluid. Alternatively, other means of separating the debris fromthe fluid can be used, such as deflection plates within the deflectortube 28 to create a spiral fluid flow, thereby separating the heavydebris from the fluid.

Another important feature of the deflector tube 28 is that its reduceddiameter facilitates movement of the cuttings along with the fluid, upto the point of separation of the cuttings from the fluid for deposit ina holding area. In a representative example, the body of the tool mighthave a nominal diameter of 75/8 inches, with the deflector tube 28having a nominal diameter of 23/8 inches. It has been found that a fluidflow velocity of approximately 120 feet per minute is required to keepthe cuttings moving along with the fluid, depending upon the fluidformulation. This flow velocity can be achieved in the exemplarydeflector tube 28 with a fluid flow rate of only about ½ barrel perminute. If a reverse circulation tool without the deflector tube 28 wereemployed, a fluid flow rate of about 6 barrels per minute would berequired to keep the cuttings moving. Put another way, if a reversecirculation tool were not used, with forward circulation instead beingrelied upon to move the cuttings all the way to the surface via theannulus, a fluid flow rate of 4 to 10 barrels per minute, or even more,would be required. This means that use of the tool of FIGS. 1 and 2allows the use of smaller pumps and motors at the well site surface, anduse of cheaper formulations of fluid.

In FIG. 1, a plurality of high speed supply fluid eductor nozzles 34 areprovided in the wash pipe ejection port section 12, with each eductornozzle 34 being aligned with one of the ejection ports 24, at a downwardangle. As the tool 8 is rotated to mill away the metal item from thewell bore with the milling tool 22, fluid is pumped by a pump (notshown) at the surface of the well site down through the workstring (notshown). The fluid flows from the workstring through the drive sub 10,and then through the eductor nozzles 34. Since the eductor nozzles 34have restricted flow paths, they create a high speed flow of fluid,which is then directed downwardly through the ejection ports 24. As thehigh speed fluid flows out of the eductor nozzles 34 and through theejection ports 24, it creates an area of low pressure, or vacuum, in thevicinity of the eductor nozzles 34, within the ejection port section 12of the separator housing.

This area of low pressure or vacuum in the ejection port section 12draws fluid up through the intake ports 26 of the milling tool 22,through the deflector tube 28, and through the screen 32. The fluidthusly drawn upwardly then passes out through the ejection ports 24 tothe annulus surrounding the separator housing, to flow downwardly towardthe milling tool 22. Excess fluid supplied via the workstring can alsoflow upwardly through the annulus toward the surface of the well site,to return to the pump.

As fluid flows past the milling tool blades 23, it entrains smallcuttings or debris generated as the blades mill away the casing or othermetal item. This debris-laden fluid then enters the intake ports 26 atthe lower end of the milling tool 22 and passes into the interior of thedeflector tube 28 within the wash pipe extension section 18. As thedebris-laden fluid exits the side ports 30 in the deflector tube 28, thedebris, which is heavier than the fluid, tends to separate from thefluid and settle into an annular area 56 between the deflector tube 28and the wash pipe extension section 18.

The fluid, which may still contain very fine debris, then flows upwardlyto contact the inlet side of the screen 32. As the fluid flows throughthe screen 32, the fine debris is removed by the screen 32, remainingfor the most part on the inlet side of the screen 32. Fluid leaving theoutlet side of the screen 32 then flows upwardly to the area of lowpressure, or vacuum, in the vicinity of the eductor nozzles 34.

This eductor nozzle of FIGS. 1 and 2 will create a sufficient flowvelocity to entrain virtually all of the small debris generated by themilling tool 22. In fact, it has been found that a 75/8 inch toolaccording to the first embodiment creates a sufficient flushing actionto remove the cutting debris from a milling operation within a 30 inchcasing.

FIG. 3 illustrates the flow scheme in the device of FIGS. 1 and 2. Arrow60 represents the pumped flow of clean fluid from the surface. That flowenters ports 34 and exits from ports 24 at an angle to the longitudinalaxis of the tool as represented by arrow 62. Upon making the exit thereis impingement against the surrounding tubular 64 as some flow goesuphole as shown by arrow 66 and some goes downhole as shown by arrow 68.The result is induced flow through the tool as indicated by arrow 70.The induced flow is also boosted by the flow represented by arrows 68heading downhole and into the lower end of the mill assembly 22. Thecuttings from the milled object 72 enter inlet 26 and mostly settle intothe annular volume 56 around the inlet tube 28.

The problem is that the circulation induced by this layout is notoptimal due mostly to the turbulence in the annular space adjacent ports24 due to impingement against the tubular 64 and the separation of thefluid streams going uphole and downhole represented by arrows 66 and 68respectively. The present invention addresses this issue with an annularpassage that has lateral ports and exterior recesses that also functionsas a centralizer. The turbulence reduction allows greater eductor flowthrough and pressure drop within the eductor to enhance the fluid drawthrough the eductor. Those skilled in the art will appreciate that otheraspects of the invention are further explained in the detaileddescription of the preferred embodiment and the associated drawingswhile recognizing that the full scope of the invention is to bedetermined by the appended claims.

SUMMARY OF THE INVENTION

A debris cleanup tool uses an eductor principle to induce flow into alower end to bring debris into a housing where the debris will eithersettle out or be screened out and the remaining fluid drawn up into theeductor with motive force for the eductor coming from clean fluid pumpeddown a tubular string from the surface. The eductor performance isenhanced with a surrounding sleeve on the eductor outlet that directseductor exhaust flow into an annular passage oriented in a downholedirection. The exterior of the sleeve has passages to allow some of theflow to go uphole while the sleeve wall has ports through it to allowflow in the annular passage to cut through to outside the sleeve forpassage uphole or downhole.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view of the upper end of a debris removal tool ofthe prior art;

FIG. 2 is a section view of the lower end of the tool shown in FIG. 1;

FIG. 3 is a circulation diagram of the flows in the tool of FIGS. 1 and2;

FIG. 4 is a section view of the present invention illustrating thepreferred flow scheme.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Interior to the housing 80 the debris removal tool shown in FIG. 4 issimilar to the design in FIGS. 1 and 2 described above. The maindifference is the shroud 82 that has a closed upper end 84 with outlet24 being closer to the closed end 84 than an open end 88 and directingflow into an annular passage 86. Passage 86 has an open downholeoriented end 88. A wall 90 has a plurality of wall openings 92 thatpreferably lead into longitudinally oriented grooves 94 that arecircumferentially spaced on the outer surface of wall 90.

Clean fluid is pumped downhole as represented by arrow 96 and exits intoannular passage 86 as the eductor exhaust stream. From there most of theflow continues down passage 86 to the lower end 88 while some of theflow goes through the openings 92. At the lower end 88 the flow splitsas indicated by arrows 98 and 100. The flow represented by arrow 98 goesto the lower end of the housing 80 to bring debris laden fluid into themill 22. The eductor 34 also draws the same fluid through the screen 32.Some of the fluid coming out of eductor 34 goes uphole through thepassages or grooves 94. Some flow can go through the wall openings 92into grooves 94 or to the outer surface of wall 90 adjacent the grooves94. The flow that gets to the bottom 98 of the passage 96 at least inpart makes a sharp hairpin turn to go through the grooves 94. Thegrooves 94 are optional and any number can be used with the crosssection being semi-circular, quadrilateral, triangular or some othershape. Alternatively to grooves the wall 90 can be made thick enough tohave longitudinal bores instead of grooves 94. As another option thewall 90 can be made thin enough and the grooves 94 can be eliminatedwhile still leaving an annular passage uphole for some of thecirculating fluid to return to the surface.

The wall openings 92 can have a variety of shapes and distributionpatterns. Their purpose is to allow some of the flow to take a short-cuton the way uphole. The holes can be a constant dimension bore or theycan be flared toward the outside of the wall 90 to reduce erosion.

Those skilled in the art will also appreciate that the shroud 82 alsofunctions as a centralizer by having an outer dimension larger than thehousing 80. As an option hard facing can be an exterior feature of theshroud 82 to reduce wear for running in and during mill operation.

Tests reveal that the presentation of the passage 86 when using theshroud 82 reduces turbulence that otherwise occurs as the exiting flowfrom the eductor 34 also reduces the total flow through the eductor.With more flow through the eductor a higher debris laden flow stream ismaintainable so that the mill 22 runs cooler and the efficiency ofdebris collection is enhanced. On the other hand the presence of theshroud 82 can also restrict flow trying to go uphole so that the groovesor passages 94 are used to offset that effect. Those skilled in the artwill recognize that an optimization of the area of the passage 86 andthe return flow to the surface represented by arrows 100 can beundertaken for a given application.

While a debris cleanup tool is illustrated the present invention hasapplication to other subterranean tools that use an eductor concept toinduce circulation.

The above description is illustrative of the preferred embodiment andmany modifications may be made by those skilled in the art withoutdeparting from the invention whose scope is to be determined from theliteral and equivalent scope of the claims below.

1. A tool for subterranean use, comprising: a housing having a passagetherethrough; an eductor located in said passage for inducing fluidcirculation through said passage, said eductor having an outlet leadingthrough a wall of said housing; a turbulence reducing member mountedadjacent said outlet to enhance the ability of said eductor to inducefluid circulation in said passage.
 2. The tool of claim 1, wherein: saidturbulence reducing member extends from said housing to allow saidmember to serve as a centralizer for said housing.
 3. The tool of claim1, wherein: said turbulence reducing member defines an annular passageabout said outlet.
 4. The tool of claim 3, wherein: said annular passagehas a closed end and an opposed open end.
 5. The tool of claim 4,wherein: said outlet is located closer to said closed end than said openend.
 6. The tool of claim 4, wherein: said turbulence reducing membercomprises a sleeve mounted to said housing where said closed end isdefined and spaced from said housing at an opposite end to define a flowoutlet.
 7. The tool of claim 6, wherein: said sleeve comprises a walldefining said annular passage, said wall having at least one openingfrom said annular passage extending therethrough and between said ends.8. The tool of claim 6, wherein: said sleeve comprises a wall definingsaid annular passage, said wall having an outer surface and at least onegroove on said outer surface.
 9. The tool of claim 8, wherein: saidgroove is substantially aligned with a longitudinal axis of saidhousing.
 10. The tool of claim 9, wherein: said groove has a rounded,quadrilateral or triangular shape in section.
 11. The tool of claim 6,wherein: said sleeve comprises a wall defining said annular passage,said wall having at least one wall passage therethrough that extendslongitudinally between said ends of said sleeve.
 12. The tool of claim11, wherein: said wall passage has a rounded, quadrilateral ortriangular shape in section.
 13. The tool of claim 8, wherein: saidsleeve comprises a wall defining said annular passage, said wall havingat least one opening from said annular passage extending therethroughand between said ends.
 14. The tool of claim 13, wherein: said openingintersects said groove.
 15. The tool of claim 13, wherein: said openingis offset from said groove.
 16. The tool of claim 11, wherein: saidsleeve comprises a wall defining said annular passage, said wall havingat least one opening from said annular passage extending therethroughand between said ends.
 17. The tool of claim 16, wherein: said openingintersects said passage.
 18. The tool of claim 17, wherein: said openingis offset from said passage.
 19. The tool of claim 1, wherein: saideductor draws debris laden fluid into said housing where at least someof said debris is captured.
 20. The tool of claim 14, wherein: saideductor draws debris laden fluid into said housing where at least someof said debris is captured.